This application is related to and claims priority from Japanese Patent Application No. 2002-179939, filed on Jun. 20, 2002.
The present invention relates to a magnet roller for use in electrophotographic devices such as copying machine, facsimile and laser printer, and a process for preparing a magnet roller.
A magnet roller which has been conventionally used in electrophotographic devices such as copying machine, facsimile and laser printer, has a plurality of magnetic poles on its surface and is scaled in a rotatable cylindrical sleeve so that the outer peripheral surface (outer surface) of the magnet roller does not come into contact with the inner peripheral surface (inner surface) of the sleeve.
Such magnet rollers are known, for instance, from JP-A-54-80755 which discloses a magnet roller for electrophotographic development using a permanent magnet body constructed by arranging block magnets around a shaft to form a plurality of magnetic poles in which a pair of adjacent two poles have the same polarity and the magnetic field strength at the intermediate position between the adjacent two poles is less than {fraction (1/10)} of that of the adjacent two poles, and JP-A-59-166977 which discloses a magnet roller prepared by a process comprising the steps of magnetizing two magnetic pole-forming portions adjacent in the circumferential direction of a roll-shaped magnetic body in the same polarity by a single electromagnet extending over these adjacent portions, and concentrically and rotatably arranging a non-polar sleeve over the peripheral surface of the roll-shaped magnetic body.
In case of an integral-type magnet roller, it is necessary to form a plurality of magnetic poles on the magnet roller body. However, it is often difficult to form a plurality of magnetic poles on the magnet roller body in various magnetic force patterns, and there is a technical limit. Therefore, for the preparation thereof has been generally adopted a method in which magnet pieces having a magnetic force and a magnetization patter which are required to each of the pieces are separately prepared and adhered to a shaft so that the prepared magnet roller has a required predetermined magnetization pattern.
As shown in FIG. 2, a conventional procedure for bonding the magnet pieces is carried out by setting a shaft to an adhesion tool for regulating the bonding position with only the side face of a base magnet piece 2a, fitting the side face of magnet piece 2a to the adhesion tool, uniformly applying an instantaneous adhesive to the inner peripheral surface (inner surface) of the magnet pieces 2a in the longitudinal direction, and immediately pressing the inner surface of the magnet piece 2a against the shaft to adhere the magnet piece 2a. Magnet pieces 2b and 2c are then adhered onto the shaft one by one with fitting the position to that of the magnet piece 2a, thus bonding and fixing the magnet pieces to form a magnet roller.
This operation is not efficient and takes a time, since the magnet pieces are uniformly coated with an instantaneous adhesive in the longitudinal direction at their sides and inside peripheral surface and adhered to each other one by one with fitting them to the position of the base magnet piece 2a. Also, since adhesion accuracy is not good, it may invite lowering of the accuracy of pole positions. Further, since excessive adhesive overflows onto the outer peripheral surface and axial direction end surface of the magnet pieces, a work to remove the overflowed adhesive is required.
A primary object of the present invention is to solve problems as mentioned above and to provide a process for preparing a magnet roller in good working efficiency and high adhesion accuracy without overflowing excessive adhesive.
Another object of the present invention is to provide magnet rollers having a small variation in magnetization pattern between the magnet rollers.
These and other objects of the present invention will become apparent from the description hereinafter.
The present invention provides:
(1) a process for preparing a magnet roller comprising a plurality of magnet pieces, the process comprising the steps of regulating the bonding position of at least two magnet pieces by their outer peripheral surfaces and a part of their side surfaces, applying an adhesive from the inner surface side of the magnet pieces to the adhesion faces of the magnet pieces for bonding one magnet piece to another magnet piece to form a magnet block, and bonding and fixing the magnet block to a shaft;
(2) a process for preparing a magnet roller comprising a plurality of magnet pieces, the process comprising the steps of applying an adhesive from the inner surface side of at least two magnet pieces to the adhesion faces of the magnet pieces for bonding one magnet piece to another magnet piece to form a magnet block, and bonding and fixing the magnet block to a shaft, wherein at least one of the facing adhesion faces of the magnet pieces have a plurality of grooves having a width of 0.1 to 2 mm and a depth of 0.1 to 0.5 mm at an interval of 0.1 to 5 mm and extending in the direction from the inner surface side of the magnet piece toward the outer surface side thereof;
(3) the process of item (2), wherein the length of the grooves formed in the adhesion face is from 15 to 95% of the thickness of the magnet piece in its radial direction, and the grooves extend from the inner surface of the magnet piece;
(4) the process of item (2) or (3), wherein the grooves are formed simultaneously with extrusion for preparing the magnet pieces;
(5) the process of item (2), (3) or (4), wherein after the bonding position of at least two magnet pieces is regulated by their outer peripheral surfaces and a part of their side surfaces, the adhesive is applied from the inner surface side of the magnet pieces to the adhesion faces of the magnet pieces to form a magnet block, and the magnet block is adhered and fixed to the shaft;
(6) the process of any one of items (2) to (5), wherein the Vickers hardness of the magnet pieces is from 5 to 150;
(7) a magnet roller comprising a plurality of magnet pieces adhered to each other in a circumferential direction at their adhesion faces to form a cylindrical body, wherein grooves having a width of 0.1 to 2 mm and a depth of 0.1 to 0.5 mm are formed in at least one of the facing adhesion faces of the magnet pieces at an interval of 0.1 to 5 mm in a direction from the inner surface side to the outer surface side of the magnet piece;
(8) the magnet roller of item (7), wherein the length of the grooves formed in the adhesion face to extend from the inner surface side of the magnet piece toward the outer surface side thereof is from 15 to 95% of the thickness of the magnet piece in its radial direction, and the grooves extend from the inner surface of the magnet piece;
(9) the magnet roller of item (7) or (8), wherein the grooves are formed simultaneously with extrusion for preparing the magnet pieces;
(10) the magnet roller of item (7), (8) or (9), which is prepared by a process comprising the steps of regulating the bonding position of at least two magnet pieces by their outer peripheral surfaces and a part of their side surfaces, applying an adhesive from the inner surface side of the magnet pieces to the adhesion faces of the magnet pieces to form a magnet block, and bonding and fixing the magnet block to a shaft; and
(11) the magnet roller of any one of items (7) to (10), wherein the Vickers hardness of the magnet pieces is from 5 to 150.
According to the present invention, the adhesion time is shortened as compared with a conventional process, so the productivity is improved. Also, since a step between adjacent two magnet pieces, which may be formed when joining magnet pieces to each other, can be decreased, variation in magnetic force is decreased to about half of that in a conventional process. Since the gap between the magnet pieces is hard to be formed, variation in angle of magnetic pole becomes small. Further, problem due to slight variation in size of magnet pieces per se is eliminated by regulating the periphery of magnet pieces when joining them, and the torsion of magnet pieces is decreased, so magnet rollers of good quality can be obtained.